F9 full search is an indexed search. This means you need to have your content indexed in order for searches of words to take place. To ensure records are indexed, you must enable the option in the settings here:
Enable the option [After any changes or additions]
You can manually perform a full index at any time with the command menu "Tools / Admin / Build Complete Full Text Index". You only need to do this once as the settings option will automatically index any new and/or modified records.
The Full Search is very fast and perfect for searching words. However, it isn't very good at searching for phrases. Searching for "note" won't find "notes" or "noting". You will need to do a slower [Search By Field] for that. Also remember that Folder Names are not indexed, only the name of Documents and its contents. I could make this an option to include it, if needed.
I hope this helps. Further information about Searching and Indexing can be found here: